Vane rings

ABSTRACT

One piece cast metal vane rings of the same shroud diameter and number of vanes but of different throat areas are made using a pattern assembled from several pattern pieces in which the vanes have different angles to the axis of the vane ring shroud. A set of pattern pieces of two or three different angles can thus provide for a number of different throat areas, thus avoiding having to prepare, in a large number of different sizes, expensive molds for making pattern pieces for molds of the same diameter but differing throat areas.

Unlted States Patent 11 1 1111 3,751,180

Cameron 1 1 Aug. 7, 1973 [541 VANE RINGS 910,266 1 1909 B6llUZZO 415 1951,525,814 2 1925 Lasche 415/195 James Mammal! Camemni 2,524,869 10 1950Adamtchik 415/216 Lambert, Quebec, Canada FOREICN PATENTS OR APPICATIONS [73] Ass1gnee: United Aircraft of Canada Limited, 766 i (r B LHS/I t J ca l'l ill 11,890 1911 (il'Cill Britain 415 195 [22 Filed; July6, 971 568,402 1 1933 ot-rmrm 415 195 Foreign Application Priority DataDec. 8, 1970 Great Britain 58,329/71) [52] US. Cl. 415/195, 415/216 [51]Int. Cl. F01d 9/02 [58] Field of Search 415/119, 195, 216, 415/217;416/223, 216, 217

[56] References Cited UNITED STATES PATENTS 3,536,417 10/1970 Stiefel eta1 416/223 3,347,520 10/1967 Owczarck 415/- 3,169,747 2/1965 Seymour415/195 2,331,076 10/1943 Meldahl 415/195 Appl. No.: 159,879

"iiiii Primary Examim'r-Henry F. Raduazo Attorney-Alan Swabey [57]ABSTRACT One piece cast metal vane rings of the same shroud di ameterand number of vanes 'but of different throat areas are made using apattern assembled from several pattern pieces in which the vanes havedifferent angles to the axis of the vane ring shroud. A set of patternpieces of two or three different angles can thus provide for a number ofdifferent throat areas, thus avoiding having to prepare, in a largenumber of different sizes, expensive molds for making pattern pieces formolds of the same diameter but differing throat areas.

4 Claims, 5 Drawing Figures mum INVENTOR James MacDonald CAMERON ATTORNEY f minnow 1m v 3.751.180 sum 2 or 2' INVEN TOR FIG 5 JamesMacDonald CAMERON VANE RINGS BACKGROUND OF THE INVENTION This inventionrelates to one-piece cast metal vane rings and their manufacture.

FIELD OF THE INVENTION The vane ring is used in the gas turbine engineto direct the exhaust gases coming from the combustion chamber of theengine onto the turbine blades. Such a ring is located, as a stator,between the combustion chamber and the first stage turbine and betweeneach subsequent turbine stage. I

The vane rings are made up of inner and outer cylindrical shroudsintervened by an annulus containing a number of vanes inclined to theaxis and equally spaced apart circumferentially so that between eachpair there is a converging passage whose minimum cross-sectional area iscalled the throat area substantially equal to the other throat areas.The sum of the throat areas of the vane rings (called the total throatarea) determines the amount of air the ring is adapted to pass.

DESCRIPTION OF THE PRIOR ART Different engines of the same model havedifferent total throat area requirements. So, it is necessary for anengine manufacturer to provide a number of vane rings of the samecircumference, having different total throat areas.

One-piece cast metal vane rings, of the type to which the inventionapplies, are made by casting them in one piece by the lost wax process.A number of different tools are required to make the wax or plasticpattern, and each time a change is made in total throat area, a new setof tools is required. For example, as many as seven tools have beenrequired to obtain the optimum total throat area for a particular enginemodel while under development and in production.

SUMMARY OF THE INVENTION The applicatn has now developed a vane ringdesign which can be produced with a limited number of tools, whileproviding a large variety of total throat areas in a vane ring of thesame circumference. In this design, instead of the respective throatareas between each pair of blades being equal as in the prior art, thereare at least two different throat areas, but the total throat areaprovides the total throat area required of the particular engine.

This is effected, according to the invention, as follows. Some of thevanes are at a different angle from the axis of the engine to othervanes, so that the trailing edges of some of the vanes are offset from aplane perpendicular to the axis of the engine as compared with thetrailing edges of adjacent vanes. Through this arrangement throat areasof different dimensions result. The total throat area is thus changed bya small increment for each vane arranged at a different angle. Thisdesign, as will be seen, greatly facilitates manufacture of vane ringsof the same circumference, having different total throat areas, whichcan be matched with different throat area requirements of the enginemodel to which the vane rings are fitted.

In making a vane ring according to prior art, a composite wax assemblyis first made by assembling together, in a holder, a plurality ofseparate, but identical, wax or plastic patterns, in a manner wellknown. The

wax patterns are made by first preparing an expensive steel mold of thedesired size and shape. An assembly fixture also has to be made.According to this procedure each time a change in total throat area hasto be made, a new set of identical patterns is required. These have tobe prepared by first making a new steel mold to be used in the proceduredescribed.

In accordance with the present invention at least two different patternsare made to provide, in turn, at least two different throat areas suchthat, when the patterns are assembled together to form the ring pattern,a predetermined total throat area is provided. By varying the number ofpatterns of each angle making up the composite ring pattern, a number ofdifferent total throat areas are possible by selecting different numbersof each vane angle pattern. By providing more than two differentpatterns having respectively different angles from the axis of theengine, a still greater number of different total throat areas can beprovided to reduce considerably the number of expensive steel moldsneeded to vary the total throat area of a ring of a given circumference,for various engine throat area requirements. The different air foilwaxes or plastic pieces are arranged so that the same assembly fixturecan be used.

BRIEF DESCRIPTION OF THE DRAWING Having thus generally described theinvention, it will be referred to, in more detail, by reference to theaccompanying drawings, illustrating preferred embodiments, and in which:

FIG. 1 is a front view of a vane ring showing the leading edges;

FIG. 2 is a rear view of a vane ring showing the trailing edges;

FIG. 3 is a cross-section along lines 33 of FIG. 1;

FIG. 4 is an elevation showing two wax or plastic pattern pieces, fittedtogether in a sub-assembly as they are in a pattern;

FIG. 5 is a front perspective view of the assembly shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly tothe drawings, FIG. 1 shows a special high temperature resistant alloycast vane.ring A made up of an outer shroud l5 and an inner shroud 17forming therebetween an annulus. Within the annulus, and extendingbetween the shrouds l5 and 17, and integrally connected thereto are anumber of spaced apart vanes 19, 21, 23, 25, etc. having respectiveleading edges 19a, 21a, etc. and trailing edges 19b, 21!), etc. Thetrailing edge of the inner shroud 17 is shown as 17a. The edge 17a isperpendicular to the axis of the vane ring. Adjacent vanes, for example,as demonstrated by the vanes 19 and 21 (FIG. 3) enclose a throat area asindicated by an arrow 22, and the adjacent vanes 21 and 23 enclose athroat area as indicated by arrow 24, while the throat area between theadjacent vanes 23 and 25 is indicated by the arrow 26.

In accordance with the invention, the throat areas vary between certainpairs of vanes. This is accomplished in accordance with the presentinvention by varying the inclination or angle of certain of the vanes ascompared with other vanes as indicated diagrammatically (exaggerated) inFIG. 3 in connection with the blades 19 and 21 so that the passagebetween the vanes is of a different minimum cross-section or throat areafrom that between vanes 21 and 23. The inclination of the individualvane is varied about a pivot point, for example shown at X on a planeparallel to the trailing edge 17a of the shroud 1'7. In FIG. 3 the vane19 is shown pivoted counterclockwise about the point X as compared tothe vanes 21 and 23 so its trailing edge 19b is slightly out of theplane of the trailing edges 21b and 23b. It will be noted, from thedrawing, that the trailing edge 19!; of the blade 19 is raised relativeto the trailing edge 17a of the inner shroud 17, as compared with thetrailing edges 21b and 23b. Likewise, the leading edge 19a is lower thanthe leading edges 21a and 23a. Consequently, the width of the passagebetween the blades 19 and 21, as shown by the arrow 22, is less than thewidth of either of the passages between the pairs of vanes 21, 23 and23, 25 respectively, as indicated by the arrows 24 and 26. So the throatarea be tween the vanes 19 and 21 is smaller than that between the vanes21 and 23.

The vane ring A is made by assembling wax or plastic pieces 28, 30, etc.and fitting them together in a fixture to produce the ring pattern whichis invested with a skin of a material which becomes the mold, as is wellknown in the investment casting art. Two pattern pieces are shown fittedtogether in a sub-assembly B. The fully assembled pattern is of the sameshape as the vane ring to be cast. According to the invention, aplurality of different shaped pattern pieces are made, that is to saypieces in which the inclination of certain of the vanes differs fromthat of other vanes. A preferred number of patterns is three, one havinga maximum vane inclination, a second, a minimum inclination and thethird an intermediate inclination. What is meant by different shapedcomposite patterns is patterns which have at least two different vaneangles and consequently provide different throat areas between vanes.

A typical example of a vane ring A is as follows. The inner shroud 17 is9 inches and the outer shroud l 12 inches in outside diameter. The vanesare approximately 1 and k inches in radial height. The required totalthroat area is 13.333 square inches. The ring A has vanes. Vanes l9 and21 of different angles are used. The angles of vanes 19 and 21 are suchthat 15 vanes would provide a total throat area of 13.035 square inchesusing vane 19 alonge and l3.630 square inches for using vane 21 alohe.One assembly, using eight of vane 19 and seven of vane 21 generated atotal throat area of 13.31 square inches. Another assembly also made upof eight vanes 19 and seven vanes 21 generated a total throat area of13.35 square inches. This variation is within an acceptable tolerancefor total throat areas, since even when making one piece cast metal vanerings by the conventional method, there is i always a certain differencein total throat area, resulting from unavoidable slight variations inthe assembly technique. This variation in total throat area is normallyacceptable when within a i l percent tolerance. The percentage throatarea difference between a ring made up entirely of vanes having themaximum angle of the vane 19 to the axis of the ring and a ring made upentirely of vanes 21 having a minimum angle to the axis of the ring isbetween about 4 percent and about 4-% percent total throat areavariation. In other words,

the mixing of wax or plastic pieces with vanes at different anglespermits this relatively wide range of variation in total throat area.

According to the invention, then, the intentional or built-in variationbetween the two or more different vane angles is considerably greaterthan any difference which may occur accidentally, even though thevariation is quite small. But, the built-in variation is great enoughthat a plurality of patterns, having different vane angles, can beassembled to provide for a number of different total throat areas,ranging from the total provided by using all patterns of the same anglewhich would provide the minimum total throat area to the total whichprovided using all patterns which would provide the maximum throat area.A great number of inbetween variations are possible by differentcombinations of the respective patterns.

The materials employed in making the vane rings of the invention arewell known in the art. For example, the vane ring itself is preferablyof a special high temperature resistant alloy. The materials used in theinvestment casting process are also well known in the investment castingart as are the techniques used. One technique'has been used toillustrate the invention and is preferred, but other techniques canequally be used.

The principle of the invention then is to classify each individual vanein its pre-investment form (wax or plastic model), select an appropriatevane class, mix and distribution, assemble, invest, etc. and cast. Thiseffectively duplicates the procedure used with individual vane segmentsprior to the introduction of the integral vane ring. By selecting atleast two vane angles, preferably at least three vane angles, a wideselection of total throat areas can be produced. By stocking wax orplastic pieces of different vane angles, the time required to obtain anew vane ring class can be greatly reduced, as it is only necessary toassemble, cast and machine.

I claim:

1. A one-piece cast metal gas-turbine vane ring, comprising,

spaced apart inner and outer annular shrouds having a common axisextending therebetween, a plurality of substantially equally spacedapart vanes of the same size, shape and aerodynamic characteristics,said vanes being inclined at a generally common angle to said axis andhaving respective trailing edges lying close to a plane perpendicular tosaid axis with each pair of vanes providing therebetween a passagehaving a particular throat area, at least one of said vanes beinginclined at a specific minimum angle to said axis and at least one otherblade being inclined at a specific maximum angle to said axis such thatthe difference between the total throat area of the vane ring if all theblades were at said minimum angle vand the total throat area of the vanering if all the'bla'des were at said maximum angle would be not lessthan 1 percent and not more than 4-% percent in the total throat areavariation. 7 2. A metal vane ring, as defined in claim 1, in which thereare vanes having at least three different angles.

3. A metal vane ring, as defined in claim 1, in which said maximum andminimum angles are such that the difference between the total throatarea of the vane ring if all the blades were at said minimum angle andthe total throat area of the vane ring if all the blades were at saidmaximum angle would be not less than 2 percent and not more than 4-1:percent in the total throat area variation.

4. A metal vane ring, as defined in claim 1, in which to said maximumand minimum angles.

l l t I I

1. A one-piece cast metal gas-turbine vane ring, comprising, spacedapart inner and outer annular shrouds having a common axis extendingtherebetween, a plurality of substantially equally spaced apart vanes ofthe same size, shape and aerodynamic characteristics, said vanes beinginclined at a generally common angle to said axis and having respectivetrailing edges lying close to a plane perpendicular to said axis witheach pair of vanes providing therebetween a passage having a particularthroat area, at least one of said vanes being inclined at a specificminimum angle to said axis and at least one other blade being inclinedat a specific maximum angle to said axis such that the differencebetween the total throat area of the vane ring if all the blades were atsaid minimum angle and the total throat area of the vane ring if all theblades were at said maximum angle would be not less than 1 percent andnot more than 4- 1/2 percent in the total throat area variation.
 2. Ametal vane ring, as defined in claim 1, in which there are vanes havingat least three different angles.
 3. A metal vane ring, as defined inclaim 1, in which said maximum and minimum angles are such that thedifference between the total throat area of the vane ring if all theblades were at said minimum angle and the total throat area of the vanering if all the blades were at said maximum angle would be not less than2 percent and not more than 4- 1/2 percent in the total throat areavariation.
 4. A metal vane ring, as defined in claim 1, in which thereis at least one vane set at an angle intermediate to said maximum andminimum angles.